The Lateral Tunnel Fontan

The right lobe of the thymus is subtotally removed to facilitate exposure and dissection of the innominate vein and SVC. The pericardium is opened in the midline. The SVC is fully mobilized, taking care not to injure the phrenic nerve. The azygos vein is also dissected and may be temporarily occluded during the anastomosis of the SVC to the pulmonary artery. The main pulmonary artery and its bifurcation, and the left and right branches, are mobilized. The ligamentum arteriosum is doubly ligated and divided. If present, any patent systemic to pulmonary artery shunts are dissected free from the surrounding tissues. Marking sutures are placed on the SVC and right pulmonary artery to facilitate proper alignment of the future anastomosis.

The ascending aorta is cannulated. The cavae are cannulated with a small right-angled cannula near the innominate vein, and a larger cannula inferiorly at the cavo-atrial junction. A tourniquet is placed around the IVC, but not yet tightened. Cardiopulmonary bypass is initiated and the patient cooled to 30°C, and the heart is kept beating. Any patent shunts should now be controlled. Further dissection is completed if necessary. IVC = inferior vena cava; RPA = right pulmonary artery; SVC = superior vena cava; v = vein.

The SVC is occluded with a vascular clamp just proximal to the cannula. If there is azygos continuity, the clamp is placed proximal to the azygos connection. A further vascular clamp is placed immediately above the cavo-atrial junction, taking care not to injure the sinus node. The SVC is transected immediately above this clamp. SA = sinoatrial; SVC = superior vena cava.

A large side-biting clamp is placed over the upper margin of the right pulmonary artery, which is incised. If a shunt is present on this site, it is disconnected and any distortion or narrowing is repaired using patch angioplasty.

An end-to-side anastomosis is then performed between the SVC and right pulmonary artery using a running 6-0 or 7-0 polypropylene. To avoid a purse-string effect and maintain a wide anastomosis, the suture line is locked in several places. In the case of bilateral SVCs, it is necessary to do bilateral cavopulmonary shunts, unless a large bridging vein is present, or one of the cavae is very small, in which case the cardiac end of this SVC can be closed. We would not routinely cannulate bilateral SVCs because of the risk of causing stenosis of the small SVCs. During the construction of the cavopulmonary anastomosis the clamp on the cephaloid end of the SVC can be intermittently released if there is concern about venous hypertension. SVC = superior vena cava.

The aorta is cross-clamped and diastolic cardiac arrest is achieved using cold blood cardioplegia. The main pulmonary artery is transected. To prevent bleeding or aneurysm formation, the proximal pulmonary artery stump is closed using a double row of running 5-0 polypropylene suture that incorporates the valve leaflets and is reinforced with two Teflon felt strips. The distal main pulmonary is closed with a autologous pericardial or Gore-Tex patch so as not to narrow or distort the branch pulmonary arteries. MPA = main pulmonary artery.

The tourniquet around the IVC is snared down. The vascular clamp on the SVC–atrial junction is released. The right atrium is opened parallel to the crest of the septum. If necessary, the intraatrial communication is enlarged to allow unobstructed pulmonary venous flow to the systemic ventricle. The length of the baffle is measured between the Eustachian valve and crista terminalis. ASD = atrial septal defect; CT = crista terminalis; EV = Eustachian valve; IVC = inferior vena cava; RA = right atrium; SVC = superior vena cava.

The intraatrial pathway is a composite tunnel made of the atrial sinus venarum and a Gore-Tex patch (A). A Gore-Tex tube of at least 16 mm diameter is cut to length, split longitudinally, and shaped (B). If required, a 4- to 5-mm fenestration is cut (C). CT = crista terminalis; EV = Eustachian valve.

The prosthetic baffle is sewn in around the upper half of the junction of the IVC with the right atrium, along the posterior wall of the atrial septum (taking care not to injure the sinus node) (A), and the crista terminalis (the prominent ridge in front of the SVC), and finally the anterior wall of the atrium (B). The coronary sinus remains outside the baffle. The atrial incision is closed with a running 5-0 polypropylene suture. ASD = atrial septal defect; IVC = inferior vena cava; SVC = superior vena cava.

The undersurface of the right pulmonary artery is incised so that an unobstructed anastomosis can be created between the intraatrial tunnel and the pulmonary artery. It may be necessary to enlarge the anastomosis with a patch plasty (inset) but care has to be taken not to compromise the sinus node or its artery. To optimize Fontan hemodynamics, the anastomosis of the inferior vena cava can be offset from the superior cavopulmonary anastomosis to direct blood preferentially into the right pulmonary artery, but this is not always possible because of the anatomical setup. The SVC stump is then anastomosed to the undersurface of the right pulmonary artery using 5-0 polypropylene. It is a mistake to simply anastomose the SVC stump to the transected pulmonary artery, as this distorts the pulmonary artery, which has to be brought out right and anteriorly. A needle vent is placed in the ascending aorta. The heart is carefully deaired, and it is particularly important to evacuate air from the right atrium, which is now part of the systemic circulation. The aortic cross-clamp is released and the patient is fully rewarmed. RPA = right pulmonary artery; SVC = superior vena cava.

A direct pressure monitoring line is placed in the pulmonary venous atrium (pulmonary artery pressure is measured via a percutaneous line in the internal jugular vein). Two atrial and two ventricular pacing wires are placed on the heart. The patient is weaned from cardiopulmonary bypass. Mediastinal and pleural drains are placed and the chest is closed. RA = right atrium; RV = right ventricle.

Limited dissection is done of the SVC, taking care not to injure the phrenic nerve. The ascending aorta is cannulated; a small right-angled cannula is placed high up in the SVC or the innominate vein, and a further venous cannula is placed at the inferior cavo-atrial junction. On cardiopulmonary bypass with moderate hypothermia, the aorta is cross-clamped and cardioplegia is infused via the aortic root. A vascular clamp is placed across the SVC and the tourniquet around the IVC is snared. Ao = aorta; IVC = inferior vena cava; MPA = main pulmonary artery; RA = right atrium; RV = right ventricle; SA = sinoatrial; SVC = superior vena cava.

The right atrial free wall is opened parallel to the atrioventricular groove, and the superior end of the incision veers anterior to the sinus node. A longitudinal incision is made on the inferior surface of the right pulmonary artery. The superior end of the atrial incision is sutured to the posterior edge of the right pulmonary artery incision using continuous 5-0 polypropylene (inset). PTFE = polytetrafluoroethylene; RA = right atrium; RPA = right pulmonary artery; SVC = superior vena cava.

The right atrial free wall is opened parallel to the atrioventricular groove, and the superior end of the incision veers anterior to the sinus node. A longitudinal incision is made on the inferior surface of the right pulmonary artery. The superior end of the atrial incision is sutured to the posterior edge of the right pulmonary artery incision using continuous 5-0 polypropylene (inset). PTFE = polytetrafluoroethylene; RA = right atrium; RPA = right pulmonary artery; SVC = superior vena cava.

A Gore-Tex baffle is cut to size, fenestrated, and sutured into the right atrium so as to direct IVC blood flow to the right pulmonary artery.

Finally, to complete the pulmonary venous atrium, the free edge of the original right atrial free wall is sutured obliquely over the anterior surface of the Gore-Tex baffle. ASD = atrial septal defect.